This invention relates to motion detectors, and in particular to the use of motion detectors to prevent injuries from occurring in connection with mobile storage units.
Mobile storage systems are widely used and well known to comprise a series of storage units which have shelves or bins, for example. Except for one or both of the end units, which may be stationary, each of the storage units will normally be movable, such as on rails, to create an access aisle between two of the units. As this aisle opens, the other units are positioned in close side-by-side relationship to minimize the overall floor space required for the units, moving together to do so. Especially in larger mobile storage units and systems, the carriages can be quite large, and the loads they carry quite heavy, such as steel or construction materials. It is necessary, therefore, to provide motorized means for moving the units. These motorized moving means in turn require the use of means for preventing adjacent units from moving together when a person or other living thing is positioned between them, so as to avoid injury or damage.
In the past it has been customary to provide a sweep or safety switch bar for notifying the control system to inhibit motion of a storage unit if the bar encounters an obstacle or impediment to movement, as shown for instance in U.S. Pat. Nos. 4,743,078 and 4,733,923, both invented by the same inventor as the present application. When such a structure is used alone to protect a person, however, the requirement of physical contact with the bar can be disconcerting and startling, which can make use of this structure alone undesirable. Use of a photoelectric sweep, as disclosed in co-pending application Ser. No. 07/697,307, filed May 8, 1991, now allowed, is only slightly less disconcerting, as the moving storage unit must still move quite close to a person before its motion is interrupted.
Another alternative is to use a "safety floor", such as set forth in U.S. Pat. Nos. 4,744,307 and 4,693,184, which disclose constructions of floor panels including safety switches. A person's weight on one of the floor panels activates one of the safety switches, which notifies the control system to inhibit movement of the storage units. While these units work very well from a safety standpoint, they can be rather expensive, resulting in their non-use in certain situations. And U.S. Pat. No. 4,745,516 even discloses the use of a safety sweep and a safety floor in combination.
Another safety device to be considered is a motion sensor positioned on the carriage, so that the movement of a person between the mobile storage units can be detected and the storage units deactivated. So as not to react to the movement of the storage units themselves, the type of motion sensor activated by a person's body heat should be used. To date, however, such motion sensors deactivate themselves as soon as a person has ceased to move, which does not necessarily mean that the person is no longer between the storage units. The person may simply have temporarily paused, such as to read something on one of the shelves.
This invention relates to improvements to the structure set forth above, and to solutions to some of the problems raised or not solved thereby.